Mashiro Amatsuki is a 17-year-old former gymnast whose career ended abruptly due to an injury shortly after beginning professional training in her second year of high school. Following her retirement, she shifted focus to seeking employment. She lives in the same apartment complex as the male protagonist and initially distrusted him after he photographed her during gymnastics practice, interpreting it as invasive behavior and creating friction between them. Their dynamic improved when he aided her job search, leading her to express sincere gratitude for his assistance. Physically, Mashiro possesses lilac-colored hair and aubergine eyes. Her everyday attire typically combines an indigo shirt with light brown shorts or a skirt. Notably, she often wears a business suit even in incongruous environments like the beach on sweltering summer days, displaying high heat tolerance despite visible discomfort such as sweating. She shares her age group with characters like Yui Hanasaka and Minori Nanahashi. Unlike Yui, who remains a high school student, Mashiro had embarked on a professional gymnastics path prior to her injury.